What are the key points of highway tunnel construction technology?

As we all know, the construction of tunnels is relatively complicated and involves many difficult technologies, which brings great difficulties to highway construction. For this reason, it is necessary to strengthen technical research, improve the control level of tunnel quality management, and improve the overall quality of highways.

Construction characteristics of highway tunnels

Double-track railway lining trolley

During highway tunnel construction, it is easily affected by natural factors and the surrounding environment. The tunnel project itself is very complicated, and some unpredictable situations may occur during construction, which makes the entire tunnel project more difficult, and the tunnel project is also very susceptible to the influence of different engineering operations. Because the space inside the tunnel project has great limitations, the entire project construction process will have a crossover phenomenon. Construction within such a narrow internal space increases the difficulty of construction. Tunnel engineering is also susceptible to geological influences. The geology of the tunnel site is generally very complicated, and conditions such as collapse are prone to occur, which also poses a great threat to engineering construction.

Key points of highway tunnel construction technology

Tunnel waterproof board laying formwork

(1) Geological exploration technology

In the detection stage, infrared or electromagnetic techniques can be used to provide early warning of areas that have not been surveyed with the help of advanced geological forecasting technology, so that construction personnel have sufficient time to respond to possible threats and can also adjust the plan in time And technology to ensure the orderly development of construction. The above-mentioned technology can effectively predict the geological conditions and water-bearing conditions of the mountains, thereby effectively ensuring engineering safety. In addition, monitoring and measurement must be carried out. Monitoring and measurement are divided into two types: mandatory measurement and selective measurement. The purpose of the mandatory test is to ensure the stability and safety of the rock during construction, the operation is relatively simple and convenient, there are more sections, and the measurement results are more reliable. The required measurement link is mainly to observe the support status and geology directly, and to measure the surface subsidence and surrounding displacement. The selective test link is a supplement to the required test link, mainly by measuring relatively special sections, and after in-depth understanding and grasping of the surrounding rock and support conditions, effective control of the support, and then providing areas without excavation reference.

(2) Anchor rod construction technology

The construction environment of the anchor rod should be kept clean, and all the rock debris and impurities in the hole near the drill hole should be removed to prevent pollution of the construction. In the construction of the anchor rod, the different functions are adapted to the different technical points. If it is the coil anchor rod, then in the actual construction, there is a sequence of insertion of the anchor rod and the medicine pack in the hole. Note The pulping link also followed closely. Since the anchor rod may still move in the hole after grouting, in order to ensure the firmness and stability of the anchor rod, steel arches or steel mesh can be used to make the anchor rod and the hole more closely connected.

(3) Concrete spraying technology

First, before spraying the concrete, it is necessary to ensure that the sprayed object is free of impurities and kept clean. If concrete and impurities are mixed with each other, the adhesion between the concrete and the sprayed object will be reduced. The target of spraying is usually the excavation section to keep clean, which can also improve the quality of the section.

Second, in the mix ratio of concrete, when designing the mix ratio, it needs to be based on actual tests. When selecting additives, it needs to match the actual configuration requirements of the concrete. The concrete link is very important. Only by using concrete that meets the design requirements can concrete really play its role. When selecting the specific method of spraying, in addition to determining according to the entire project situation, it is also necessary to pay attention to changes during the actual construction. It cannot be fixed and needs to be adjusted according to the actual construction situation.

Third, pay attention to spraying continuously, not intermittent spraying. After choosing the right method, you also need to choose a high-quality sprayer, and do a good job of mixing the concrete to ensure that it is evenly distributed in the section.

(4) Waterproof and drainage construction technology

In this link, deep-buried water ditches can be used to drain the water that may seep out of the tunnel. When designing drainage, consider whether the water body may be frozen. Waterproof technology can be used in the open tunnel section, generally using water barrier and waterproof layer to prevent water leakage. In deformation joints or construction joints where leakage may occur, it should be prevented in advance, and rubber waterstops can be installed to avoid leakage. Also set up drainage pipes at appropriate locations so that water can flow out of the tunnel and into the surrounding rivers or lakes.

(5) Tunnel body excavation technology

The excavation of the hole is mainly the excavation of the middle pilot hole and the left and right holes. For the pilot tunnel, trenching must be strictly carried out in accordance with the set contour line. After the initial spraying of concrete, a steel grille arch shall be installed, and then it shall be connected with the steel grille outside the hole to make it a whole. The cyclic footage generally ranges from 0.5 to 1.2m. After the excavation is formed, the centerline and level must be strictly inspected. If both meet the relevant requirements, it is necessary to spray 0.05m thick C25 strength grade concrete. The soil excavated on the upper steps can be manually turned to the lower steps, and then transported out using machines and cars. To excavate the annular pilot pit and then to dig the middle core, it is generally necessary to make the middle core within the interval of 1.6 to 2m from the vault.

Tunnel construction quality control measures

Tunnel waterproof board laying formwork

(1) Ensure the quality of drawings

Drawing design is the foundation of tunnel engineering, and good drawings are essential to the entire project. When controlling the quality of the project, we must first start from the drawings, try to minimize the phenomenon of changing drawings, and then reduce the changes in the construction process. Changes in drawings or construction will bring great hidden dangers. For this reason, it is necessary to conduct detailed studies on drawings before construction to ensure design quality. When designing the drawings, it is necessary to make preparations to conduct detailed surveys of the geological environment, hydrology, weather and other conditions around the construction site to ensure the accuracy of the data, and then design scientific and reasonable drawings to lay the foundation for construction. When reviewing drawings, a layered review mode should be used. The person in charge of the project should communicate well with the designer to ensure that the design meets the project requirements and promote the smooth development of the project.

(2) Improve construction technology

The construction unit needs to truly understand that in order to effectively improve the quality of the tunnel project, it needs to develop and improve the construction technology, strengthen the learning of new technologies, and apply them in the actual process. Of course, this application also needs to be in line with the actual engineering. Combine each other, learn from each other’s strengths, and ensure that the technology is reasonable. For example, the method of arching first and then wall is common in tunnel engineering, especially in some fault-fractured areas or places with very complicated geological conditions. However, advances in science and technology have increasingly highlighted the backwardness of this method, which has been unable to meet the requirements of tunnel construction. , Gradually replaced by the step method. The step method has many advantages in construction, which can effectively improve the stability of the tunnel, ensure the safety of the tunnel, and to a certain extent can shorten the entire project practice, thereby effectively reducing the project cost. For this reason, it is necessary to continuously research and develop various new technologies in accordance with the development requirements of the times to improve construction efficiency and promote the development of the industry.

(3) Reasonably allocate engineering resources to ensure safety

In order to effectively apply various technologies and ensure the use effect, we must also pay attention to other factors in the project, such as the quality of materials required for construction, or the performance and usage of construction equipment, etc. These essential resources in construction are essential Construction technology has an important impact. In construction, the reasonable allocation of various resources and the quality of the resources themselves are very important, which is an important part of ensuring the quality of the project. The various materials required in the construction should be started from the source, the quality of the materials should be strictly checked, and the inspection should be done. If the quality is unqualified, it should be replaced in time. Also pay attention to the storage of materials, such as explosives that may be used in tunnel construction, need to be strictly managed, and stored in a clean area, kept dry to prevent it from being unusable due to dampness, and also pay attention to fire prevention and avoid mismanagement And cause an explosion and so on. In daily life, we must do a good job in the maintenance and repair of equipment, and we must not wait for the equipment to be broken before thinking of repairs. We must ensure that the equipment can provide support for the implementation of the technology and make the project proceed in an orderly manner.

(4) Strengthen later detection

It is necessary to adopt advanced detection technology to detect tunnel entities, guide the on-site defect remediation, and enhance the safety and usability of tunnel engineering. For example, advanced tunnel compactness testing equipment and geological radar testing equipment, etc., the use of various advanced technologies needs to make it effective, optimize the inspection quality, and determine the width of the roadway in the tunnel, the total width of the tunnel, For inspection of clear height, etc., it is also necessary to inspect the hollow and thickness of the tunnel lining, the actual strength of the concrete, and the grouting situation to ensure that all contents meet the relevant requirements. It is necessary to ensure that the inspection quality is qualified, strengthen the construction of quality levels, make the inspection results more real and effective, ensure that the project is qualified for acceptance, and ensure the quality of the project.

In short, the construction of highway tunnels is complicated, cumbersome and difficult. It needs to be paid attention to by relevant personnel, combined with the actual characteristics of the project, design drawings that meet the requirements, select appropriate processes, strictly manage the materials required for the project, and strengthen personnel supervision. Continuously develop various new processes. Particular attention should be paid to the construction details. Since the tunnel involves many complicated processes, any small detail error may bring a major threat to the entire project. Therefore, we must pay more attention to improve the construction quality of the project to ensure the safety and stability of the tunnel.